1. Field of the Invention
The present invention relates to a flexible flat cable for low voltage differential signaling (LVDS), and more particular to a flexible flat cable including a conductive line having a circular sectional surface at a central part thereof, and flat upper and lower surfaces at a terminal part thereof.
2. Description of the Related Art
U.S. Patent Application No. 2013-0037303 discloses “flexible flat cable”. The flexible flat cable includes a plurality of conductive lines arranged in parallel and an insulating layer to cover the conductive lines. The flexible flat cable disclosed in U.S. Patent Application No. 2013-0037303 has cutting lines to divide the conductive lines covered with the insulating layer into several strips and stack the conductive lines to reduce the width of the flexible flat cable. However, in the conductive line, the terminal part is formed by pressing a terminal part of a metallic wire having a circular sectional surface through a rolling process and making the terminal part of the metallic wire flat, and exposed to the outside.
Accordingly, when wiring is performed between electronic devices using the flexible flat cable, the stacked part of the conductive line has a circular sectional surface so that the stacked part of the conductive line has flexibility, and the connection part of the conductive line has a flat surface in order to improve rolling workability and securely ensure the connection when connecting the electronic devices with each other.
A flat cable employing a conductive line having a flat terminal part formed by pressing a terminal part of a metallic wire having a circular sectional surface through a rolling process is disclosed in Japanese Unexamined Patent Publication No. 2010-192287. The flat cable disclosed in Japanese Unexamined Patent Publication No. 2010-192287 has a structure in which conductive lines having circular sectional surfaces are arranged in parallel, upper and lower portions of the conductive lines are covered with insulators, terminal parts of the conductive lines are exposed, and the exposed terminal parts of the conductive lines having the circular sectional surfaces are pressed through the rolling process, so that the terminal part have the upper and lower surfaces.
In addition, a structure in which flat terminal parts are formed by pressing conductive lines having a circular section surface through the rolling process and arranged in parallel is disclosed in Japanese Unexamined Patent Publication No. 2002-56721. According to Japanese Unexamined Patent Publication No. 2002-56721, a user may arbitrarily select a conductor having a circular sectional surface or a flat conductor for use.
U.S. Patent Application No. 2012-0205138 discloses a flexible flat cable in which terminal parts of conductive lines having circular sectional surfaces are pressed through the rolling process so that flat terminal parts are formed and the conductive lines are arranged in parallel. According to the flexible flat cable of U.S. Patent Application No. 2012-0205138, before covering conductive lines having circular sectional surfaces, which are arranged in parallel, with upper and lower insulating films, portions of the conductive lines having the circular sectional surfaces are pressed through rolling process so that flat portions of the conductive lines are formed and exposed at an end of the flexible flat cable, and upper and lower insulating films are covered on the conductive lines.
If the rolling process is performed to make a metallic wire having a circular sectional surface flat, a part of the metallic wire subject to the rolling process loses the inherent flexibility of the metallic wire and becomes rigid. The terminal part that loses the flexibility and becomes rigid may have a low bending characteristic, that is, low flexibility. Accordingly, when the terminal part is bent, the terminal part may be easily broken. If the terminal part is broken, a signal cannot be exactly transmitted, so that a device cannot be operated or the operating error of the device may occur. In particular, a flexible flat cable having a terminal to be directly inserted into a connector without a PCB substrate may more severely represent the above phenomenon. In order to remove the above problems, the terminal part must have a predetermined degree or of flexibility. A pure copper wire requires 10% or more of flexibility and 0.2 kgf or more tension.